Biomedical body electrode

ABSTRACT

A biomedical body electrode is provided having a nonconductive housing with an apertured face for application to a body surface. A metallic element is mounted within the housing, the element and the face defining a cavity therein. An electrolyte fills the cavity and a membrane is secured to the face to cover the apertures, thereby sealing the electrolyte within the cavity. A lead is connected to the metallic element for connecting the electrode to external instrumentation.

United States Patent [1 1 3,590,810

[721 inventor Milos T. Kopecky .085.577 4/1963 Berman et al 128/418LittletomColo. l 1l 619 /1964 Sullivan 128/417 [21] Appl. No. 732.145 '1187.745 6/1965 Baum et al 128/206 [22] Filed May27 1968 3.253.595 5/1966Murphy etalr 128/405 Patented July 6, 197] 3,295.515 1/1967 Kahn.....1.l28/2.06 [73] Assignee Honeywell lnc. 3.394.069 7/1968 Solomons. 204/195Mineapolis, Minn. 1.429 785 2/1969 Ross 204/1 3,464,404 9/1969 Mason .1l28/2.06

54 BIOMEDlCAL BODY ELECTRODE Primary Examiner-Richard A. Gaudet 8 Chims,2 Drawing p Assistant Examiner-G. F. Dunne 52 us. Cl 1280.06,A'wmeyhmhur Swanson and l28/4l7,204/l95 1 l hlflcl it a ABSTRACT: Abiomedical body electrode is provided having Field 01 Search v .1 128/2.2.06. a nonconductive housing with an apertured face for applica- 1 1405.4104! v tion to a body surface. A metallic element is mounted within1 31 2 6. the housing, the element and the face defining a cavityReferences Cited therein. An electrolyte fills the cavity and a membraneis secured to the face to cover the apertures, thereby sealing theUNlTED STATES PATENTS electrolyte within the cavity. A lead is connectedto the metal- 3,492,216 1/1970 Riseman... 128/201 (X) lic element forconnecting the electrode to external instru- 2,782,786 2/1957Krasno..... 128/417 mentation.

MEMBRANE PATENTED JUL 6197i FIG.

IIIIIIIIIIII 1111111111: 11111111,

MEMBRANE INVENTOR. M l LOS T. KOPECKY ATTORNEY.

BIOMEDICAL BODY ELECTRODE The present invention relates to electrodes,and more particularly to an improved electrode for application to a bodysurface. Such electrodes, commonly called body electrodes, are used withelectromedical diagnostic and therapeutic apparatus, such aselectrocardiographs, pacemakers and other devices, as input and outputterminals for transferring electrical signals to and from a living body.

One early form of body electrodes comprised a metallic plate secured indirect contact with a patients skin. Such an electrode however, hadseveral distinct drawbacks, a first being that the metal plate-to-skincontact of the electrode generated unwanted contact potentials. A seconddrawback with this form of electrode was that even the slightestmovement between the metal plate of the electrode and the patients skincaused substantial variations in the contact impedance of the electrode,these contact impedance variations being commonly known in the medicalprofession as motion artifacts.

In order to eliminate contact potentials generated by directmetal-to-skin contact, body electrodes were subsequently developed inwhich a metallic plate or element was positioned in spaced relation to apatients skin. To establish electrical contact with the patients body,these latter electrodes required the application of a layeroftelectrolyte, in the form of a paste or gel, to that area of the bodysurface to which the electrode was to be applied. The electrolytethereby provided the electrical conductive path between the electrodesmetallic plate and the patient's body. This type of electrode, however,was very sensitive to mechanical disturbances of the electrolytematerial at the metal-electrolyte interface as resulted from motion ofthe electrode on the patients skin, and motion artifacts were producedas a consequence thereof.

Aside from motion artifacts, use of these latter electrodes had theadded disadvantage that skin irritation often resulted therefrom. Thisskin irritation caused patient discomfort and resulted since patientsskins were frequently quite sensitive or allergic to the layer ofelectrolyte paste or gel which necessarily had to be applied with theuse of these electrodes. In order to minimize such patient discomfort,in certain cases it was necessary to periodically relocate the point ofelectrode at tachment, and in certain other instances it was evennecessary to limit the use of therapeutic or diagnostic apparatusrequiring the attachment of body electrodes to a patient's body.

In is accordingly, an object of the present invention to provide animproved body electrode which, in situ, does not irritate a patientsskin, has a low and stable contact impedance which is substantiallyunaffected by motion artifacts, and generates contact potentials whichare negligible.

It is a further object of the present invention to provide bodyelectrode as set forth, suitable for use in a dynamic environmentwherein a patient may perform physical activities characterized by beinglightweight, inexpensive to manufacture, and readily attachable to apatient's body for comfortable wear.

In accomplishing these and other objects, there has been provided inaccordance with the present invention a body electrode having anonconductive housing with a metallic element mounted therein. With theelectrode in situ on a patients body surface, the housing supports themetallic element in spaced relation to the patients skin. The spacewithin the housing between the metallic element and the patients skin isfilled with an electrolyte, and the electrolyte is sealed in the housingby means of a membrane secured across a face of the housing. The face ofthe housing contacts the patients skin when the electrode is situ and anelectrical conductive path is established from the patients skin throughthe membrane, through the electrolyte, and to the metallic element ofthe electrode.

A better understanding of the invention may be had from the followingdetailed description when read in connection with the accompanyingdrawings in which:

FIG. 1 is a view of the base of an electrode according to the presentinvention, with the line 2-2 denoting the plane on which FIG. 2 istaken; and

FIG. 2 is an exploded vertical section view of the electrode of FIG. 1.

Referring to the drawings in more detail, there is shown a housing 1having a base or face 2, apertures 3 in the base 2, and a top surface 4.The top surface 4 has a small opening therein to accommodate the passageof an electrical lead 5. Mounted within the housing 1 in parallel spacedrelation to the base 2, and adjacent to the top surface 4 is a metallicelement 6. The lead 5 is connected to the upper surface of the metallicelement 6, as shown in the FIG. 2. A cavity in the housing 1 is defined,respectively, on its upper and lower boundaries by the metallic element6 and the base 2, and the cavity is filled with a suitable electrolyte16. It is here noted that in FIG. 1, the periphery of base 2 isindicated by the dotted circle 11. Further, it is noted that in anelectrode constructed in accordance with the present invention, thehousing 1 may be made of a nonconductive lightweight material, such as aplastic, and the metallic element 6 may be a silver/ silver chloridetablet of the type described in US. Pat. No. 3, I 37,29] issued toPhipps et al.

A membrane 7 and annulus or attaching means 8 are adhered to theelectrode base by a suitable adhesive. The membrane 7 is impermeable tothe electrolyte l6 and is so secured to the base 2 to cover theapertures 3, thereby sealing the electrolyte 16 within the housing 1. InFIG. 1, the periphery of the membrane 7 is indicated by the dottedcircle 9, and the inner and outer periphery of the annulus 8 areindicated, respectively, by the solid circles 10 and 15, the annulus 8surrounding the area of the membrane 7 covering the apertures 3. Theannulus 8 has an adhesive surface on the side thereof to be applied to apatients body surface or skin 17. Thereby the elec trode when in situwill adhere to the patients body as a result of the action of thisadhesive surface of the annulus 8. The electrode may be stored with aprotective covering, not shown, placed over the annulus 8 and themembrane 7 in order to protect the membrane 7 and to prevent theadhesive surface of the annulus 8 from drying prior to electrode use.While in the electrode described herein, the annulus 8 was used asattaching means to attach the electrode housing 1 to the patient's body,other attaching means known in the art could easily be substitutedtherefor, e.g. a suitable belt may be used to strap the electrode to thepatients body.

Before application of an electrode constructed in accordance with thepresent invention to the patient's body surface, the membrane 7 may bewetted with a selected wetting agent which permeates the membrane 7, andwhich is electrically conductive or will-become conductive upon contactwith the patients skin 17. Thereby the conductivity of the membrane 7 isenhanced, and it is insured that a low resistance path will be offeredto current flowing between the electrolyte 16, and the patients skin 17.In an exemplary electrode, the membrane 7 was polytetrafluorethyleneimbedded with fiber glass and a drop of water was used as the selectedwetting agent to wet the membrane 7 to enhance its conductivity. Water,if it is not already conductive due to the presence of impurities,becomes conductive upon contact with the body salts present on thepatients skin. After wetting the membrane 7, the base 2 of the electrodemay be then applied to the skin 17 with the annulus 8 serving to securethe electrode thereto. The membrane 7 which is flexible, conforms withthe patients body surface, thereby making smooth and continuous contactwith the skin 17, even in a dynamic environment in which the patient isperforming bodily activities. The lead 5 of this electrode may then beconnected to diagnositc or therapeutic apparatus, as desired, whereuponelectrical signals may be transferred to or from the patients body.

While with the exemplary electrode the membrane therein was dampenedwith a drop of water in order to enhance its conductivity, thisprocedure may not be necessary in all situations. For example with abody surface already wet, such as from a patients perspiration it maythen be unnecessary to further dampen the membrance.

Thus, there has been provided an improved body electrode which makeselectrical contact with a patients body surface by means of a flexiblemembrane which conforms to the body surface. The improved body electrodeprovides an electrical contact with the patients skin characterized by alow and stable contact impedance which is substantially unaffected bymotion artifacts, the generation of minimal contact potentials, and itsnonirritating effect on the patient's skin. Further, the improvedelectrode is lightweight, inexpensive to manufacture due to itssimplicity, and readily attachable to a patients body for comfortablewear. The ease of attachment and lightweightedness of this electrode,coupled with its low and stable contact impedance substantiallyunaffected by motion artifacts, makes this electrode suitable for use indynamic environments wherein a patient is performing physicalactivities.

The embodiments of the invention in which I claim an exclusive propertyor privilege are defined as follows:

1. An electrode for establishing electrical contact with a body surfaceof a living organism, said electrode comprising:

a nonconductive housing having a face at one end for contacting saidbody surface, said face having an aperture therein;

a metallic element mounted at the other end within said housing inspaced parallel relation to said face whereby said metallic element andsaid face define a cavity within said housing;

an electrolyte filling said cavity; a membrane secured to said face tocover said aperture, said membrane being impermeable to said electrolytethereby to seal said electrolyte within said housing, said membrancebeing permeable to at least one selected wetting agent, for dampeningsaid membrane whereby to enhance the electrical conductivity thereof;and

an electrical lead connected to said metallic element for connectingsaid electrode to external instrumentation.

2. The electrode as recited in claim 1 wherein said face has a pluralityof apertures therein, and said membrance is secured to said face tocover all of said several apertures.

3. The electrode as recited in claim 1 including means for attachingsaid electrode to said body surface.

4. The electrode as recited in claim 3 wherein said attaching meanscomprises an annulus, said annulus being secured to said facesurrounding the area of said membrance covering said aperture whereby toexpose said membrane area to said body surface, said annulus having anadhesive surface on the side thereof to be applied to said body surface.

5. The electrode as recited in claim 1 wherein said membrane ispolytetrafluorethylene embedded with fiber glass.

6. The electrode as recited in claim 5 wherein said housing innonconductive plastic and said metallic element is a silver silverchloride tablet.

7. The electrode as recited in claim 6 wherein said face has a pluralityof apertures therein and said membrance is secured to said face to coverall of said several apertures.

8. The electrode as recited in claim 7 including means for attachingsaid electrode to said body surface, said attaching means comprising anannulus, said annulus being secured to said face surrounding the area ofsaid membrance covering said apertures whereby to expose said membranearea to said body surface, said annulus having an adhesive surface onthe side thereof to be applied to said body surface.

1. An electrode for establishing electrical contact with a body surfaceof a living organism, said electrode comprising: a nonconductive housinghaving a face at one end for contacting said body surface, said facehaving an aperture therein; a metallic element mounted at the other endwithin said housing in spaced parallel relation to said face wherebysaid metallic element and said face define a cavity within said housing;an electrolyte filling said cavity; a membrane secured to said face tocover said aperture, said membrane being impermeable to said electrolytethereby to seal said electrolyte within said housing, said membrancebeing permeable to at least one selected wetting agent, for dampeningsaid membrane whereby to enhance the electrical conductivity thereof;and an electrical lead connected to said metallic element for connectingsaid electrode to external instrumentation.
 2. The electrode as recitedin claim 1 wherein said face has a plurality of apertures therein, andsaid membrance is secured to said face to cover all of said severalapertures.
 3. The electrode as recited iN claim 1 including means forattaching said electrode to said body surface.
 4. The electrode asrecited in claim 3 wherein said attaching means comprises an annulus,said annulus being secured to said face surrounding the area of saidmembrance covering said aperture whereby to expose said membrane area tosaid body surface, said annulus having an adhesive surface on the sidethereof to be applied to said body surface.
 5. The electrode as recitedin claim 1 wherein said membrane is polytetrafluorethylene embedded withfiber glass.
 6. The electrode as recited in claim 5 wherein said housingin nonconductive plastic and said metallic element is a silver silverchloride tablet.
 7. The electrode as recited in claim 6 wherein saidface has a plurality of apertures therein and said membrance is securedto said face to cover all of said several apertures.
 8. The electrode asrecited in claim 7 including means for attaching said electrode to saidbody surface, said attaching means comprising an annulus, said annulusbeing secured to said face surrounding the area of said membrancecovering said apertures whereby to expose said membrane area to saidbody surface, said annulus having an adhesive surface on the sidethereof to be applied to said body surface.